The present invention relates to a defect inspection apparatus and method and, particularly, to an apparatus of measuring a precipitated particle in a semiconductor wafer and a crystal defect, such as a stacking fault, and to a wafer surface extraneous substance inspection apparatus.
As the integration of an LSI (large scale integrated) circuit is being increased, decrease in a conforming item acquisition ratio and decrease in reliability caused by a failed MOS (metal oxide semiconductor) transistor composing the LSI circuit becomes a big problem. As causes of the failed MOS transistor, dielectric breakdown of a gate oxide film and excessive current leak in a junction are typical problems. It is not preferable that a crystal defect is formed in a surface area having elements in a silicon wafer because a failed MOS transistor occurs, as described above.
Therefore, defect measurement is important in the quality control of silicon crystal. In regard to the method measuring such a defect, there is a method in which an infrared ray transmissible through the silicon is irradiated and the scattered light is detected.
Crystal defects exist and are distributed at any positions inside a single crystal. In general, in manufacturing devices such as IC or the like, it is required to develop a wafer which does not have any crystal defect within a range from the crystal surface (mirror surface) to a level of 0.5 xcexcm depth and contains high density defects in the deep zone.
In developing such a wafer, it is necessary to observe these crystal defects to reflect the observed result to the development. In regard to the observing method, there is described a technology in xe2x80x9cExtended Abstracts of the 1996 International Conference on Slid State Devices and Materials, Aug. 26-29, 1996xe2x80x9d and xe2x80x9cApplied Physics, Vol. 65, No. 11 (1996)xe2x80x9d, pages 1162-1163.
In such a prior art, two kinds of light beams, each having a different wavelength which has different characteristics relating to absorption degree of silicon wafer, are irradiated on a silicon wafer, light scattered from a crystal defect inherent in the silicon wafer is detected and is analyzed, thereby the distribution situation of the crystal defect is indicated, or the total number of the crystal defects in a predetermined depth from the surface of the wafer is measured and is indicated.
When the crystal defect inherent in the silicon wafer is observed, and it is analyzed, the distribution situation of these crystal defects and the total number of the crystal defects in every depth from the surface of the wafer are very important factors, and the crystal defect display device for displaying these defects brought results in its own way.
The inventors of the present invention, however, foresaw that it is extremely important that the crystal defect display device display what kind of particle size and how many of the crystal defects are distributed in the respective predetermined depth positions of the silicon wafer.
For example, in the case of hydrogen anneal heat treatment, progress conditions of the heat treatment are distinguished by observing what kind of particle size and how much sludge of SiO2 are distributed in the predetermined depth position of the silicon wafer. By such an observation result, heat treatment conditions, such as temperature and treatment time in the hydrogen anneal heat treatment, can be decided ideally.
Moreover, COPs (Crystal Originated Particles) with many parts which are indistinct in its generating behavior till now are traces of the grown-in defects that remained as pits on the surface of the silicon wafer, and analysis of the most suitable condition of the process that does not produce COPs can be done easily if it can be observed how deep the defects are distributed in the silicon wafer.
In such a prior art, two kinds of light beams having different wave length which has different characteristics relating to absorption degree of silicon wafer are irradiated on a silicon wafer, light scattered from crystal defect to inhere in the silicon wafer is detected and is analyzed, thereby distribution situation of the crystal defect is indicated, or total number of the crystal defect in a predetermined depth from the surface of the wafer is measured and is indicated.
In this way, an object of the present invention is to provide a crystal defect inspection apparatus which makes it possible to observe what kind of particle size and how many of the crystal defects are distributed in various predetermined depths of the silicon wafer.
In order to attain the above objects, the present invention provides a defect inspection apparatus for detecting defects existing on a surface of a sample and/or inside the sample based on light information from the sample obtained by irradiating a light beam onto the sample, which comprises a detecting means for detecting positions in the depth direction where the defects exist and distribution of the defects based on the light information; a setting means for setting a position in the depth direction where defects exist; and a means for displaying the distribution of the defects obtained by the detecting means, the displaying means displaying the distribution of the defects corresponding to the position in the depth direction set by the setting means.
By providing the defect inspection apparatus as described above, defects for which the cause of defect occurrence is different depending on the position in the depth direction, can be selectively displayed by setting a specified position in the depth direction.
FIG. 1 is a schematic diagram showing the construction of a defect inspection apparatus in accordance with the present invention.
FIG. 2 is a chart showing timing acquiring a scattered light signal.
FIGS. 3A, 3B, 3C are relational diagrams showing detectable range by the scattered light signal.
FIGS. 4A, 4B, 4C, 4D are figures showing examples of a selective display of defect distribution.
FIG. 5 is a view showing an example of an at-a-glance display of defect distribution.
FIG. 6 shows a flowchart for being performed in the computer 6 and for outputting the defect information obtained by setting the depth of the defects.